Subject: Re: Trying to kexec on Allwinner A80

From: Russell King - ARM Linux admin <[email-masked]>
Date: Tue, 7 Apr 2020 11:19:12 +0100

On Tue, Apr 07, 2020 at 11:02:03AM +0100, Russell King - ARM Linux admin wrote:
> On Mon, Apr 06, 2020 at 10:27:20AM +0200, Corentin Labbe wrote:
> > Hello
> > 
> > I am trying to add the last missing Allwinner Soc in kernelci: the A80.
> > But this SoC does not have any way to be used in kernelci, no USB nor network in uboot.
> > So I have tried to fake uboot since the kernel has network support and run the new kernel via kexec.
> > 
> > But kexec 2.0.18 fail to work:
> > kexec --force /tmp/kernel --initrd /tmp/ramdisk --dtb /tmp/dtb --command-line='console=ttyS0,115200n8 root=/dev/ram0 earlycon=uart,mmio32,0x7000000 ip=dhcp'
> 
> As I mentioned in my other reply, this apparent "kexec" command line
> does not seem to reflect the arguments you actually used to invoke
> the kexec output below.
> 
> > syscall kexec_file_load not available.
> 
> This message is produced by do_kexec_file_load().  This function is only
> invoked if the do_kexec_file_syscall flag in main() is set.  This flag
> is only set if one of:
> 
> 	--kexec-file-syscall
> 	--kexec-syscall
> 	--kexec-syscall-auto
> 	-s
> 	-c
> 	-a
> 
> are provided on the kexec command line.  Your command line above does
> not contain any of those arguments, so either the command line is not
> what you used, or you are using a patched kexec, or your compiler is
> grossly miscompiling kexec.
> 
> > Try gzip decompression.
> > kernel: 0xb6535008 kernel_size: 0x853200
> > MEMORY RANGES
> > 0000000020000000-000000009fffffff (0)
> 
> Then there's the debug output, which is only produced if the
> kexec_debug global is set, which in turn is only set if --debug or -d
> is supplied on the kexec command line - which again, your kexec
> command line does not contain this.
> 
> > zImage header: 0x016f2818 0x00000000 0x00853200
> > zImage size 0x853200, file size 0x853200
> > zImage requires 0x00864200 bytes
> >   offset 0x0000bae4 tag 0x5a534c4b size 8
> > Decompressed kernel sizes:
> >  text+data 0x0158b3a0 bss 0x000632f0 total 0x015ee690
> > Resulting kernel space: 0x01def5a0
> > Kernel: address=0x20008000 size=0x01def5a0
> > Initrd: address=0x21df8000 size=0x0090b6fa
> > DT    : address=0x22704000 size=0x00005c09
> > kexec_load: entry = 0x20008000 flags = 0x280000
> > nr_segments = 3
> > segment[0].buf   = 0xb6535008
> > segment[0].bufsz = 0x853204
> > segment[0].mem   = 0x20008000
> > segment[0].memsz = 0x854000
> > segment[1].buf   = 0xb5c29008
> > segment[1].bufsz = 0x90b6fa
> > segment[1].mem   = 0x21df8000
> > segment[1].memsz = 0x90c000
> > segment[2].buf   = 0x4db50
> > segment[2].bufsz = 0x5c09
> > segm[   71.039126] kexec_core: Starting new kernel
> > ent[2].mem   = 0[   71.044712] Disabling non-boot CPUs ...
> > x22704000
> > segment[2].memsz = 0x6000
> > [   71.489070] Bye!
> > 
> > 
> > I have tried also kexec-2.0.20
> > Try gzip decompression.
> > zImage header: 0x00000000 0x000019b4 0x00001000
> > zImage requires 0x008641c0 bytes
> > Could not find a free area of memory of 0x86c1c0 bytes...
> > Cannot load /tmp/kernel
> 
> kexec 2.0.20 doesn't appear to have changed anything to do with how
> allocations are done.  The above output looks even more strange and
> confusing.  "zImage header" is produced by debugging prints, which
> imply that kexec_debug was set.
> 
> However, the "MEMORY RANGES" output is missing - this has not gone
> away with kexec 2.0.20, it's still there, and works for me (I've
> just built and tested kexec 2.0.20).
> 
> Also, the values on the "zImage header" line are completely messed
> up; the first should be the zImage magic value and it is not - that
> suggests that the file being loaded is not a zImage file, or is
> corrupted.

Under a VM (the kernel doesn't have kexec support - but that's not a
problem, because the initial loading stages are the relevant parts
which all happen in userspace):

# build/sbin/kexec --version
kexec-tools 2.0.20
# build/sbin/kexec --debug --load virt-vmlinuz-5.4.0+
Try gzip decompression.
kernel: 0xb6a6c008 kernel_size: 0x407358
MEMORY RANGES
0000000040000000-000000007fffffff (0)
zImage header: 0x016f2818 0x00000000 0x00407358
zImage size 0x407358, file size 0x407358
zImage requires 0x00418358 bytes
  offset 0x00007178 tag 0x5a534c4b size 12
Decompressed kernel sizes:
 text+data 0x00c2ed24 bss 0x000319ec total 0x00c60710
Resulting kernel space: 0x0104707c
Kernel: address=0x40008000 size=0x0104707c
DT    : address=0x41051000 size=0x00100000
kexec_load: entry = 0x40008000 flags = 0x280000
nr_segments = 2
segment[0].buf   = 0xb6a6c008
segment[0].bufsz = 0x40735c
segment[0].mem   = 0x40008000
segment[0].memsz = 0x408000
segment[1].buf   = 0xb696b008
segment[1].bufsz = 0x100000
segment[1].mem   = 0x41051000
segment[1].memsz = 0x100000
kexec_load failed: Function not implemented
entry       = 0x40008000 flags = 0x280000
nr_segments = 2
segment[0].buf   = 0xb6aa0008
segment[0].bufsz = 0x40735c
segment[0].mem   = 0x40008000
segment[0].memsz = 0x408000
segment[1].buf   = 0xb699f008
segment[1].bufsz = 0x100000
segment[1].mem   = 0x41051000
segment[1].memsz = 0x100000
#

On a SolidRun Hummingboard2 (iMX6 based, which has kexec support, same
kexec binary, first without an initrd, and then with):

# build/sbin/kexec --version
kexec-tools 2.0.20
# build/sbin/kexec --debug --load multi-vmlinuz-5.6.0+
Try gzip decompression.
kernel: 0xb6763008 kernel_size: 0x7273a8
MEMORY RANGES
0000000010000000-000000004fffffff (0)
zImage header: 0x016f2818 0x00000000 0x007273a8
zImage size 0x7273a8, file size 0x7273a8
zImage requires 0x007383a8 bytes
  offset 0x00004da8 tag 0x5a534c4b size 12
Decompressed kernel sizes:
 text+data 0x00dbedb8 bss 0x007489f8 total 0x015077b0
Resulting kernel space: 0x015077b0
Kernel: address=0x10008000 size=0x015077b0
DT    : address=0x11511000 size=0x0000b000
kexec_load: entry = 0x10008000 flags = 0x280000
nr_segments = 2
segment[0].buf   = 0xb6763008
segment[0].bufsz = 0x7273ac
segment[0].mem   = 0x10008000
segment[0].memsz = 0x728000
segment[1].buf   = 0x1207cb0
segment[1].bufsz = 0xb000
segment[1].mem   = 0x11511000
segment[1].memsz = 0xb000
# build/sbin/kexec --unload
# build/sbin/kexec --debug --load multi-vmlinuz-5.6.0+ --initrd /boot/initrd.img-5.4.0+
Try gzip decompression.
kernel: 0xb65d8008 kernel_size: 0x7273a8
MEMORY RANGES
0000000010000000-000000004fffffff (0)
zImage header: 0x016f2818 0x00000000 0x007273a8
zImage size 0x7273a8, file size 0x7273a8
zImage requires 0x007383a8 bytes
  offset 0x00004da8 tag 0x5a534c4b size 12
Decompressed kernel sizes:
 text+data 0x00dbedb8 bss 0x007489f8 total 0x015077b0
Resulting kernel space: 0x015077b0
Kernel: address=0x10008000 size=0x015077b0
Initrd: address=0x11510000 size=0x0053f46a
DT    : address=0x11a50000 size=0x0000b044
kexec_load: entry = 0x10008000 flags = 0x280000
nr_segments = 3
segment[0].buf   = 0xb65d8008
segment[0].bufsz = 0x7273ac
segment[0].mem   = 0x10008000
segment[0].memsz = 0x728000
segment[1].buf   = 0xb6098008
segment[1].bufsz = 0x53f46a
segment[1].mem   = 0x11510000
segment[1].memsz = 0x540000
segment[2].buf   = 0x993cf0
segment[2].bufsz = 0xb044
segment[2].mem   = 0x11a50000
segment[2].memsz = 0xc000

On clearfog (Armada 388):

# build/sbin/kexec --debug --load multi-vmlinuz-5.6.0+
Try gzip decompression.
kernel: 0xb6745008 kernel_size: 0x7273a8
MEMORY RANGES
0000000000000000-000000003fffffff (0)
zImage header: 0x016f2818 0x00000000 0x007273a8
zImage size 0x7273a8, file size 0x7273a8
zImage requires 0x007383a8 bytes
  offset 0x00004da8 tag 0x5a534c4b size 12
Decompressed kernel sizes:
 text+data 0x00dbedb8 bss 0x007489f8 total 0x015077b0
Resulting kernel space: 0x015077b0
Kernel: address=0x00008000 size=0x015077b0
DT    : address=0x01511000 size=0x00007be3
kexec_load: entry = 0x8000 flags = 0x280000
nr_segments = 2
segment[0].buf   = 0xb6745008
segment[0].bufsz = 0x7273ac
segment[0].mem   = 0x8000
segment[0].memsz = 0x728000
segment[1].buf   = 0x1be7f68
segment[1].bufsz = 0x7be3
segment[1].mem   = 0x1511000
segment[1].memsz = 0x8000

All appears to work fine.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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